This invention relates generally to the assembly of coil springs of the type used in bedding and upholstery and, more particularly, to an improved machine for fabricating coil spring assemblies.
It is well known to fabricate a coil spring assembly from a plurality of coil springs organized in matrix-like fashion into columns and rows. Often the coil spring rows are interconnected in both the top and bottom planes of the assembly. The rows and columns of the matrix are held in spatial relation in the finished assembly by some type of fastener or tie, for example, a lacing wire, that interconnects adjacent springs throughout the matrix one with the other. The helical lacing wire extends from one edge to the opposite edge of the spring assembly between adjacent rows of that assembly. The lacing wire connects adjacent springs within adjacent rows simply by being wound around the juxtaposed lacing legs or end turns of the adjacent springs. After fabrication of the coil spring assembly, manufacture of a finished product is completed by placing a cushion or pad of material, e.g., woven or non-woven batting, foam rubber, or the like, over the top and/or bottom surface of the spring assembly matrix so formed, and then enclosing that structure with an upholstered fabric or cloth sheath or the like to provide a finished saleable product. One basic use of such coil spring assemblies is in the bedding industry where those assemblies find use as mattresses or box springs, but other uses are in the home finishing industry where the finished coil spring assembly may be used in a chair""s seat or a chair""s backrest or the like.
An automatic machine for assembling continuous coil spring rows is also known. Such a machine initially picks up a row of coil springs by inserting pickup blades within the spring""s barrel and moving the spring through a 90xc2x0 arc onto a support surface. The row of springs is then compressed against the support surface, and thereafter, the row of springs is pushed between upper and lower die boxes by upper and lower rotating transfer fingers. Assuming a row of coil springs had previously been loaded in the die boxes, upper and lower clamping dies are closed to secure lacing legs of respective top and bottom turns of the two rows of coils. A helical lacing wire is then wound around the clamped lacing legs of the two rows of coils to connect the two rows of coils together. After the two rows of coil spring rows are connected, upper and lower indexing hooks grab the connected coils and index them in a downstream direction so as to permit a next row of springs to be fed between the upper and lower die boxes and connected to the assembly. When a desired number of rows of springs have been connected, a feed-out mechanism is cycled to move the completed spring assembly away from the machine.
The known coil spring assembly machine has a feed conveyor for delivering coil springs to the pickup blades for each row of coils. The feed conveyor grips the coil at a location intermediate the coil ends and orients the coil horizontally so that the coil centerline is aligned with one of the pickup blades. The pickup blades are translated into the barrels of respective coils, and then, the pickup blades are pivoted 90xc2x0 to a vertical position. The pivoting motion removes the coils from the feed conveyor and locates a row of coils on a support surface. While the above coil spring pickup mechanism works satisfactorily, it does have some disadvantages. First, as a pickup blade translates into a barrel of a coil, it passes across a path of the feed conveyor that moves in a direction perpendicular to the path of the pickup blade. Therefore, if, for any reason, the feed conveyor moves prior to the pickup blade initiating its pivoting motion, the feed conveyor would hit the pickup blade and potentially damage the pickup blade and supporting arm. Thus, there is a need for a device that receives a coil spring from a feed conveyor in a manner that does not cross the path of the feed conveyor.
The pickup blade has another disadvantage. Its length must accommodate the length of the coil as well as the length of the reciprocating stroke and the actuator that provides that stroke. Therefore, the pickup blade and supporting arm can be 24 inches or more in length. That substantial length not only increases the footprint of the machine and consumes valuable manufacturing space, but it also further separates a machine operator from a coil assembly portion of the machine. Therefore, if there is any problem or adjustment around the lacing machine in the coil assembly portion of the machine, the length of the pickup blade and supporting arm make it very difficult for the machine operator to reach in and service that area. Thus, there is a further need for a device that receives a coil spring from the feed conveyor and pivots the coil spring up to the support surface but is substantially smaller than known pickup blades.
Further, the known coil assembling machine has a pair of clamping dies for each coil location in the two rows of coil springs that are being laced together. Thus, there may be a dozen or more pairs of dies across a width of a platen that must be operated together. Each pair of dies is pivoted in a scissors style about a common pivot. The upstream or front dies of each pair of dies are opened or lowered, and the downstream or rear dies of each pair of dies are raised or closed as a coil is fed into the dies. Thereafter, the front dies are pivoted to a closed position to clamp the end turns of the coils in the two adjacent rows of coils between the two dies while the helical lacing wire is wrapped around lacing legs of respective coil springs. After the two rows of coils have been laced together, all of the dies are pivoted to an open position and the laced rows of coils are indexed forward without any interference between the rows of coils and the dies. The rear dies are then closed while the front dies remain open for reception of the next row of coils.
While the above die mechanism effectively secures the coil springs during the lacing process, it does have some disadvantages. The requirement of having the two dies in each pair of dies pivot up to a common plane places a significant demand on the die mechanisms. Thus, the die mechanisms must be constantly monitored and adjusted, if necessary, to maintain them in proper operating condition.
The above die mechanism has another disadvantage that relates to its pivoting motion. If any of the coil springs are not perfectly located, it may interfere with the rear die closing position. Thus, the rear die will strike the coil spring before it has finished its pivoting motion, and an upwardly angled force is applied against the end turn or loop of the coil spring. That force is reacted by the hood portion of the front die. After repeated applications of such an angled force, the hood of the front or rear dies often break. Thus, there is a need for a die mechanism that requires less maintenance and that repeatedly and reliably closes to its desired horizontal position, so that the creation of nonhorizontal forces is minimized.
The known coil assembly machine has a further disadvantage in not being able to automatically assemble coaxial coils. In many innerspring structures, it is desirable that some areas of the innerspring structure have a different stiffness or firmness than other areas. In one application, an increased firmness in a selected area is provided by utilizing a coil within a coil design in which a pair of coils, that is, an inner coil and an outer coil, are used to provide a coil unit having a greater stiffness. When one or more rows of such pairs of coils are laced together, they will provide an area of the innerspring structure that has an increased firmness. Thus, there is a need for a coil assembly machine that has the capability of handling and assembling rows of coils that have multiple coil springs in the row.
Consequently, there is a need for a coil spring assembly machine that not only is free of the disadvantages of known machines but is capable of handling and assembling coaxial coil springs.
The present invention provides a coil spring assembly machine that is capable of providing a spring structure of a matrix of coil springs that has areas of different firmness or stiffness. The coil spring assembly machine of the present invention is capable of forming one or more rows of coaxial coils along with rows of single coils. The coil spring assembly machine of the present invention is more reliable in operation and provides greater operator access in the event of a jam or other error condition. Thus, the coil spring assembly machine of the present invention is especially useful in manufacturing innerspring structures for furniture.
According to the principles of the present invention and in accordance with the described embodiments, the invention provides an apparatus for assembling coil springs together into a matrix of coil springs. The apparatus has workholders with respective grippers that receive and hold portions of end turns of respective coil springs, and a loader supporting the workholders for moving the workholders through a motion that transfers the respective coil springs from a conveyor to the apparatus. In one aspect of this embodiment, the portions of the end turns are resiliently secured in the grippers. By holding the end turns of the coils when moving the coils from a conveyor to the apparatus, the workholders and loader have an advantage of being substantially smaller than known devices that perform the same function. The smaller size permits better access to a lacing portion of the apparatus.
In another embodiment of the invention, the coil assembling apparatus has, for each coil, a die set having a fixed die and a movable die. The movable die is connected to a drive via linkage. The drive is operable to move the movable die through a motion that maintains a second planar die face of the movable die substantially parallel to a first planar die face of the stationary die. In one aspect of this embodiment, the linkage is a four-bar linkage and a toggle. This embodiment has an advantage of not requiring any adjustment by the user. In addition, the parallel motion of the die faces provides a more reliable and proper alignment of the coil springs within the dies and minimizes the likelihood of die breakage. The use of a toggle provides a further advantage of reacting the load of the closed dies instead of the toggle drive mechanism.
In a further embodiment of the invention, the coil assembling apparatus is operable to automatically assemble two rows of coil springs into a row of coaxial coil springs. The apparatus has a die set for each coil spring in the row of coil springs and a plurality of lifters, wherein each lifter is mounted adjacent a different one of the die sets. The lifters are movable to lift an upstream leg of an end turn of a first coil spring in the first row of coil springs that is located in a respective die set. Lifting the upstream leg of the first coil in the first row of coils permits a downstream leg of an end turn of a first coil spring in a second row of coil springs to be moved below the upstream leg of the first coil spring of the first row of coils. This interweaving of the legs of the end turns of the coil springs permits the formation of a row of coaxial coil springs from the coil springs in the first and second rows. In one aspect of this invention, the lifter is a lifter wheel with a lift cam. By lacing together rows of coaxial coils with rows of single coils, the firmness of a resulting coil spring structure can be readily varied.
In still further embodiments of the invention, methods associated with the above-described embodiments are also provided.
These and other objects and advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein.